Polymerizable ink composition, ink cartridge containing the same, and inkjet printer

ABSTRACT

A polymerizable ink composition contains polymerizable monomers containing at least one of an acrylic acid ester compound, a methacrylic acid ester compound, an acryl amide, and a methacryl amide; and a vinyl ether compound; and one of potassium oxide and sodium oxide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is based on and claims priority pursuant to 35U.S.C. §119 to Japanese Patent Application No, 2012-255915, filed onNov. 22, 2012, in the Japan Patent Office, the entire disclosure ofwhich is hereby incorporated by reference herein.

BACKGROUND

1. Technical Field

The present invention relates to a polymerizable ink composition, an inkcartridge containing the polymerizable ink composition, and an inkjetprinter.

2. Background Art

In the field of inkjet printing, the field of industrial inkjet printingin particular, curable inkjet ink has been diffusing in terms ofquick-drying, wide variety of printing substrates (recording media), andbeing free from volatile organic compounds (VOC).

Curable inkjet ink contains unsaturated organic compounds polymerizedby, for example, exposure to electron beams or ultraviolet ray under thepresence of a photopolymerization initiator. Such curable inkjet inkproduces radicals upon irradiation of energy and the unsaturated organiccompounds come to have high molecular weights by the radical reaction.As a result, the ink is fixed by curing or solidification. This reactioninstantly proceeds upon irradiation of energy, which results in quickdrying.

In addition, since curable inkjet ink is solidified immediately, the inkcan be printed on a non-ink absorbing print substrate (recording medium)that does not absorb ink such as metal, glass, china and porcelain,ceramics, or plastic film without degradation of the quality of image,resulting in a wide selection of print substrates.

Furthermore, since the entire of the unsaturated organic compoundsbecome large polymers, the printing process using this ink is VOC-free.

As the unsaturated organic compound (hereinafter referred to as monomer)of curable inkjet ink, (meth)acrylic acid ester compounds are used ingeneral. Most of such (meth)acrylic acid ester compounds are viscous.Typically, ink using a multi-functional (meth)acrylic acid estercompound having a number of polymerizable functional groups has a highcross-linking density and forms images hard to remove. However, the inktends to be highly viscous, which makes it difficult to overcome atrade-off between lowering the viscosity of a curable inkjet ink andimproving the curing property thereof.

In attempts to solve this problem, JP-2010-509426-A discloses a curableinkjet composition that can prevent curing inhibition caused by oxygenand improve attachability by adding a monomer having an epoxy groupcured by a cation, a cationic photopolymezation initiator, and water.

JP-2008-507598-A discloses ink that can form high definition images athigh speed because the curing speed thereof is improved by setting eachcontent of an unsaturated ethylene mono-functional monomer, anunsaturated ethylene di-valent monomer, an unsaturated ethylenemulti-valent monomer, and a urethane ethylene oligomer in particularranges.

JP-2009-272609-A discloses a curable composition that contains acompound having a methacroyl group or acroyl group that is able toprevent clogging of nozzles caused by curing of ink, a compound having athermocuring functional group such as a hydroxyl group or a carboxylicgroup, and a dilution agent such as a vinyl ether or an ethylenederivative.

JP-2010-530922-A discloses ultraviolet ray curable ink that improvesattachability to polypropylene or a non-porous substrate having a lowsurface tension by adding a monoacrylate having a glass transitiontemperature Tg to improve the flexibility of ink layers.

JP-2007-231230-A, JP-2007-231232-A, and JP-2008-68516-A disclose inkcompositions that improve the attachability between a recording mediumand ink by adding an ester or amide of (meth)acrylic acid, a vinyl etherhaving a hydrocarbon group, and a polymerization initiator.

JP-3672651-B1 (JP-H09-183927-A) discloses an ultraviolet ray curingresin composition for inkjet recording that forms images on paper or aplastic substrate without forming a resin layer for attachment bysetting the mass ratio among a (meth)acrylate compound, a vinyl ethercompound, and a photopolymerization initiator in a particular range.

JP-2009-62541-A, JP-2005-532445-A, and JP-2004-526820-A disclose inkhaving a quick curing speed and a low viscosity, which can be obtainedby using α,β-unsaturated ether together with a (meth)acrylate monomer.

In general, most of (meth)acrylic acid ester compounds are toxicpotential about skin sensitization that cause an allergy by touching(one of reaction of delayed hypersensitivity that causes irritated skinby excessive immune reaction to a chemical material). That is, ifnon-cured monomer compositions remain on a printed matter, it may causean allergy by touching with a finger or a hand. For this reason, inkthat forms safe printed matters without causing an allergy is desired.

However, as described above, in addition to the trade-off betweenlowering the viscosity of a curable inkjet ink and improving the curingproperty thereof, manufacturing ink having no or little skinsensitization problem is extremely difficult. In fact, the skinsensitization problem is not considered in the patent documentsmentioned above.

In an attempt to solve this problem, JP-2012-251123-A discloses aphotopolymerizable inkjet ink containing a (meth)acrylate and/or a(meth)acrylamide, and a vinyl ether compound, which has an excellentcuring property and a low viscosity without skin sensitization. Althoughthis is successful to some degree, the storage stability thereof is notfound to be satisfactory.

Furthermore, 2013-040280-A discloses an addition of water or a tertiaryamine compound to improve storage stability.

SUMMARY

The present invention provides an improved polymerizable ink compositioncontains polymerizable monomers containing at least one of an acrylicacid ester compound, a methacrylic acid ester compound, an acryl amide,and a methacryl amide; and a vinyl ether compound; and one of potassiumoxide and sodium oxide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an example of the ink bag ofan ink cartridge according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram illustrating an example of the inkcartridge according to an embodiment of the present disclosure in whichthe ink bag of FIG. 1 is accommodated; and

FIG. 3 is a schematic diagram illustrating an example of an inkjetrecording device (printer) according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

JP-2012-251123-A discloses a photopolymerizable inkjet ink containing a(meth)acrylate and/or a (meth)acrylamide, which has an excellent curingproperty and a low viscosity without skin sensitization. Although thisis successful to some degree, the storage stability thereof is not foundto be satisfactory.

As a result of an investigation made by the present inventor to improvethe storage stability of this ink, it has been found that the storagestability is not improved by just using (adding) a conventionally andwidely used radical polymerization inhibitor, for example, phenolquinone compound such as hydroquinone and methoquinone as apolymerization initiator for optical polymerizable inkjet ink containinga (meth)acrylate compound.

Furthermore, JP-2013-040280-A discloses an addition of water or atertiary amine compound to improve storage stability. The storagestability was evaluated under the acceleration test conditions at 70° C.for 4 days and the result was no change of appearance.

Moreover, the present inventor has found that, instead of or in additionto these materials, the storage stability of the polymerizable inkjetink can be furthermore improved by addition of a strong alkali component

In view of the foregoing, the present invention is to improve thephotopolymerizable (curable) inkjet ink described in JP-2012-251123-Amentioned above and provide a low viscous polymerizable ink compositionhaving an excellent curability and storage stability while being freefrom skin sensitization problems.

The polymerizable ink composition of the present disclosure is describedin detail.

The polymerizable ink composition of the present disclosure contains atleast a polymerizable monomer. The polymerizable monomer is at least oneof an acrylic acid ester compound, a methacrylic acid ester compound, anacryl amide, and a methacryl amide; and a vinyl ether compound. Thepolymerizable monomer also contains a strong alkali component. At leastone of the at least one of an acrylic acid ester compound, a methacrylicacid ester compound, an acryl amide, and a methacryl amide preferablyhas 1 to 6 functional groups.

As the (meth)acrylic acid ester compound or the (meth)acryl amidecompound, known compounds can be used. It is preferable to use acompound having a Stimulation Index (SI) of less than 3, which indicatesthe degree of sensitivity as measured by a skin sensitization testaccording to Local Lymph Node Assay (LLNA) Method.

The skin sensitization test of LLNA method is defined in OECD testguideline 429. For example, if the SI values is less than 3, no skinsensitization problem occurs as shown in “Function and Materials”(published in September, 2005, Vol. 25, No. 9, P55-P64). In the materialsafety data sheet (MSDS), a material evaluated as no skin sensitizationor negative naturally has an SI value less than 3. Therefore, such amaterial has considered to be free from such a skin sensitizationproblem.

The polymerizable ink composition of the present disclosure preferablycontains a polymerizable monomer having an SI value of less than 3,which makes this polymerizable ink composition safe with regard to skinsensitization. If this is the case, a non-cured monomer component thatremains on a printed matter does not cause an allergy when it is touchedby a finger. That is, a safe printed matter is provided.

Specific examples of (meth)acrylic acid ester compounds or (meth)acrylamide compounds easily and economically available on market and freefrom the skin sensitization problem include, but are not limited to,polyethylene glycol dimethacrylate represented by a chemical formula 1:CH₂═C(CH)₃CO—(OC₂H₄)_(n)—OCO—C(CH₃)═CH,  Chemical formula 1(n is from 9 to 14, where n represents an average polymerizationdegree), γ-butylolactone methacrylate, trimethylol propanetrimethacrylate, tricyclodecane dimethanol dimethacrylate,caprolactone-modified dipenta erythritol hexaacrylate, polypropyleneglycol diacrylate represented by the following chemical formula 2,CH₂═CH—CO—(OCH₃H₆)_(n)—OCOCH═CH₂,  Chemical formula 2a diacrylate of caprolactone modified hydroxy pivalic acid neopentylglycol ester represented by the following chemical formula A:

where m and n represent average polymerization degrees and m+n=4,polyethoxylated tetramethylol methane tetraacrylate, ethyleneoxide-modified bisphenol A diavrylate, neopentyl glycol dimethacrylate,stearyl acrylate, 1,4-butane diol dimethacrylate, and hydroxyethyl acrylamide.

In addition, the following (meth)acrylates or (meth)acryi amides can beused in combination unless causing a problem as ink although these arenot suitable more or less about skin sensitization.

Specific examples of (meth)acrylate and (meth)acryi amide that can beused in combination with (meth)acrylates or (meth)acryi amides free fromthe skin sensitization problem include, but are not limited to, ethyleneglycol (meth)acrylate, hydroxy pivalic acid neopentyl glycoldi(meth)acrylate, γ-butylolactone acrylate, isobornyl(meth)acrylate,formalized trimethylol propane mono(meth)acrylate, polytetramethyleneglycol di(meth)acrylate, trimethylol propane (meth)acrylic acidsalicylic acid ester, diethylene glycol di(meth)acrylate, triethyleneglycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate,polyethylene glycol diacrylate [(CH₂═CH—CO—(OC₂H₄)n-OCOCH═CH₂ (n=4)],polyethylene glycol diacrylate [(CH₂═CH—CO—(OC₂H₄)_(n)—OCOCH═CH₂ (n=9)],polyethylene glycol diacrylate [(CH₂═CH—CO—(OC₂H₄)_(n)—OCOCH═CH₂(n=14)], polyethylene glycol diacrylate[(CH₂═CH—CO—(OC₂H₄)_(n)—OCOCH═CH₂ (n=23)], dipropylene glycoldi(meth)acrylate, dipropylene glycol di(meth)acrylate, polypropyleneglycol dimethacrylate [(CH₂═C(CH₃)—CO—(OC₃H₆)_(n)—OCOC(CH₃)═CH₂ (n=7)],1,3-butane diol di(meth)acrylate, 1,4-butane diol diacrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonene diol di(meth)acrylate, neopentylglycol di(meth)acrylate, tricyclodecane dimethanol diacrylate,di(meth)acrylate of an adduct of bisphenol A with propylene oxide,1,6-hexane diol di(meth)acrylate, polyethylene glycol di(meth)acrylate,dipenta erythritol hexa(meth)acrylate, methacryloyl morphorine,2-hydroxyethyl methacryl amide, ethylene oxide-modified tetramethylolmethane tetramethacrylate, dipentaerythritol hydroxypenta(meth)acrylate,caprolactone-modified dipentaerythritol hydroxy penta(meth)acrylate,ditrimethylol propane tetra(meth)acrylate, pentaerythritoltetra(meth)acrylate, trimethylol propane triacrylate, ethyleneoxide-modified trimethylol propane tri(meth)acrylate, propyleneoxide-modified trimethylol propane tri(meth)acrylate,caprolactone-modified trimethylol propane tri(meth)acrylate,pentaerythritol tri(meth)acrylate, tris(2-hydroxyethyl)isocyanulatetri(meth)acrylate, neopentyl glycol diacrylate, ethoxylated neopentylglycol di(meth)acrylate, propoxylated neopentyl glycol di(meth)acrylate,propoxylated glyceryl tri(meth)acrylate, polyester di(meth)acrylate,polyester tri(meth)acrylate, polyester tetra(meth)acrylate, polyeterpenta(meth)acrylate, polyester poly(meth)acrylate, vinylcaprolactam,vinyl pyrrolidone, N-vinyl formamide, polyurethane di(meth)acrylate,polyurethanetri(meth)acrylate, polyurethane tetra(meth)acrylate,polyurethane penta(meth)acrylate, polyurethane hexa(meth)acrylate,dimethyl(meth)acryl amide, dimethyl aminopropyl(meth)acryl amide(DMAPAA), isopropyl(meth)acryl amide (NIPAM), and diethyl(meth)acrylamide (DEAA).

A specific example of vinyl ether compound free from skin sensitizationis triethylene glycol divinyl ether. Since this vinyl ether compound islow viscous, it is possible to lower the viscosity of ink and improvethe curability thereof without skin sensitization in comparison with acase in which no vinyl ether compound is used.

However, as described later, it is preferable to use a photoradicalpolymerization initiator for the ink composition of the presentdisclosure. In addition, since a vinyl ether compound is notsignificantly radical-polymerization reactive, if it is blendedexcessively to lower the viscosity of ink, curability greatly suffersfor lowering the viscosity. Therefore, the content of a vinyl ethercompound is preferably from 5% by weight to 60% by weight and morepreferably from 30% by weight to 50% by weight in a polyemrizablemonomer taking into account the balance between low viscosity andcurability.

The polymerizable ink composition of the present disclosure contains astrong alkali component.

The content of the strong alkali component depends on the solubility ofpotassium oxide or sodium oxide in materials. The content of strongalkali component in ink depends on what kind of a (meth)acrylic acidester compound or a (meth)acryl amide compound is used and the ratio ofan added vinyl ether compound. In terms of the balance between curingspeed after energy irradiation and storage property, the content ispreferably from 0.0001 parts by weight to 0.5 parts by weight to 100parts by weight of a polyemrizable monomer and more preferably from0.001 parts by weight to 0.1 parts by weight.

Not all of polymerizable monomers having SI values of less than 3dissolves potassium hydroxide or sodium hydroxide quickly. For example,triethylene glycol vinyl ether and (meth)acrylic acid ester compounds or(meth)acryl amide compounds having hydrophillic structure are highlyhydrophillic. Therefore, it is efficient to use an aqueous solution ofpotassium hydroxide or sodium hydroxide in terms of quick dissolution ofpotassium hydroxide or sodium hydroxide.

In the present disclosure, whether a strong alkali is dissolved or notis determined by visually confirming that the liquid is uniform andtransparent in a state in which no coloring agent such as a pigment iscontained.

As the polymelization initiator, it is possible to use a photoradicalpolymerization initiator or a photocation polymerization initiator. Itis suitable to use a photoradical polymerization initiator. The reasonis as follows: (Meth)acrylic acid ester compounds are generally radicalpolymerizable and also cation polymerizable but photoacationpolymerization initiators are expensive in general and gradually producestrong acids without irradiation of light. For this reason, selection ofmembers contacting ink such as ink supplying paths in a printer islimited. Moreover, although UV-LED has become popular in recent years asan energy-efficient light source, UV-LED available on market is only 365nm or longer. Unfortunately, (meth)acrylic acid ester compounds are notsufficiently sensitive in such a long frequency range.

Specific examples of photoradical polymerization initiators include, butare not limited to, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl propane-1-one,1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one,2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-1-propane-1-one,phenyl glyoxylic acid methyl ester,2-methyl-1-[4-(methylthio)phenyl]-2-morpholino propane-1-one,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholino-4-yl-phenyl)butane-1-one,bis(2,4,6-trimethylbenzoyl)-phenyl phosphine oxide,bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentyl phosphine oxide,2,4,6-trimethyl benzoyl-phosphine oxide, 1,2-octanedione-[4-(phenylthio)-2-(o-benzoyloxime], {ethanone,1-[9-ethyl-6-(2-methyl benzoyl)-9H-carbazole-3-yl]-1-(o-acetyloxime)]},[4-(methylphenylthio)phenyl]phenyl methanone, benzophenone, methylbenzophenone, methyl-2-benzoyl benzoate, 4-benzoyl-4′-methyldiphenylsulfide, phenyl benzophenone, 2,4-diethylthioxanthone,2-chlorothioxanthone, isopropylthioxanthone, and1-chloro-4-propylthioxanthone. The content of the polymerizationinitiator is preferably from 1 part by weight to 20 parts by weight to100 parts of a polyemrizable monomer.

The polymerizable ink composition of the present disclosure contains aconventional radical polymerization inhibitor.

Specific examples of such radical polymerization inhibitors include, butare not limited to, 4-methoxy-1-naphthol, methyl hydroquinone,hydroquinone, t-butyl hydroquinone, methoquinone, di-t-butylhydroquinone,2,2′-dihydroxy-3,3′-di(α-methylcyclohexyl)-5,5′-dimethyldiphenylmethane, p-banzoquinone, 9,10-di-n-buthoxy anthracene, and4,4′-[1,10-dioxo-1,10-decanediylbis(oxy)]bis[2,2,6,6-tetramethyl]-1-piperidinyloxy.

The polymerizable ink composition of the present disclosure may containa coloring agent. Any known inorganic pigment or organic pigment can beused. Carbon black manufactured by a furnace method or a channel methodcan be used as a black pigment.

Specific examples of the white pigments include, but are not limited to,sulfates of alkali earth metals such as barium sulfide, carbonates ofalkali earth metals such as calcium carbonates, silicas such as finepowder of silicic acid and synthetic silicate, calcium silicate,alumina, hydrated alumina, titanium oxide, zinc oxide, talc, and clay.

Pigment Yellow pigments can be used as yellow pigments.

Specific examples thereof include, but are not limited to, PigmentYellow 1, Pigment Yellow 2, Pigment Yellow 3, Pigment Yellow 12, PigmentYellow 13, Pigment Yellow 14, Pigment Yellow 16, Pigment Yellow 17,Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 75, Pigment Yellow83, Pigment Yellow 93, Pigment Yellow 95, Pigment Yellow 97, PigmentYellow 98, Pigment Yellow 114, Pigment Yellow 120, Pigment Yellow 128,Pigment Yellow 129, Pigment Yellow 138, Pigment Yellow 150, PigmentYellow 151, Pigment Yellow 154, Pigment Yellow 155, and Pigment Yellow180.

Pigment Red pigments can be used as magenta pigments.

Specific examples thereof include, but are not limited to, Pigment Red5, Pigment Red 7, Pigment Red 12, Pigment Red 48 (Ca), Pigment Red48(Mn), Pigment Red 57 (Ca), Pigment Red 57:1, Pigment Red 112, PigmentRed 122, Pigment Red 123, Pigment Red 168, Pigment Red 184, Pigment Red202, and Pigment Violet 19.

Pigment Blue pigments can be used as cyan pigments.

Specific examples thereof include, but are not limited to, Pigment Blue1, Pigment Blue 2, Pigment Blue 3, Pigment Blue 15, Pigment Blue 15:3,Pigment Blue 15:4. Pigment Blue 16, Pigment Blue 22, Pigment Blue 60,Pat Blue 4, and Pat Blue 60.

Considering properties, other inorganic pigments and organic pigmentscan be suitably used.

The polymerizable ink composition of the present disclosure preferablyhas a viscosity of 3 mPa·s to 200 mPa·s at 25° C. However, there areinkjet discharging heads available on market (for example, GEN4,manufactured by Ricoh industry Company Ltd.) which can be heated to 60°C. and discharged under 20 mPa·s or less. Therefore, it is not necessarythat the viscosity is within this range if the viscosity is loweredsufficiently by heating.

The polymerizable ink composition of the present disclosure can beapplied by, for example, spray coating. Also, the polymerizable inkcomposition of the present disclosure can be applied to an inkjetapparatus (inkjet printer), etc.

Ink using the ink composition of the present disclosure can beaccommodated in a container for an ink cartridge. Due to such an inkcartridge, there is no need to directly touch ink during operations suchas ink change, which makes users free from concerns of contamination onfingers and clothes and also prevents foreign objects such as dust frommingling into ink.

There is no specific limit to the container. Any form, any structure,any size, and any material can be suitably selected. For example, acontainer having an ink bag formed of aluminum laminate film, a resinfilm, etc. can be suitably used.

Next, the ink cartridge is described in detail with reference to FIGS. 1and 2. FIG. 1 is a schematic diagram illustrating an example of an inkbag 241 in the ink cartridge of the present disclosure and FIG. 2 is aschematic diagram illustrating an ink cartridge 200 that accommodatesthe ink bag 241 of FIG. 1 in a cartridge housing 244.

As illustrated in FIG. 1, after the ink bag 241 is filled with ink froman ink inlet 242 and the air remaining in the ink bag 241 is discharged,the ink inlet 242 is closed by fusion. When in use, the ink is suppliedby piercing the needle provided to the inkjet recording device into anink outlet (243) made of rubber. The ink bag 241 is formed of apackaging material such as aluminum laminate film having no airpermeability.

As illustrated in FIG. 2, the ink bag 241 is accommodated in thecartridge housing 244 made of plastic. Theses are detachably attached tothe inkjet recording apparatus as the ink cartridge 200.

It is particularly preferable that the ink cartridge of the presentdisclosure is detachably attachable to the inkjet recording device ofthe present disclosure. By using the ink cartridge, replenishing andexchanging ink is simplified, thereby improving the workability.

FIG. 3 is a schematic diagram illustrating an example of an inkjetrecording device (printing apparatus) related to the present disclosure.The inkjet printing device (inkjet printer) includes a printing unit anda radiation source irradiation unit. The configuration and form of theprinting apparatus is not limited to this embodiment.

FIG. 3 is a diagram illustrating an example in which color images areformed by a printing unit 3 (3 a, 3 b, 3 c and 3 d of each color, forexample, yellow, magenta, cyan, and black) from which each color ink isejected onto a print substrate (recording medium) 2 fed from a printsubstrate supplying roll 1 followed by irradiation of UV ray emittedfrom ultraviolet ray light sources (radiation source irradiation unitsfor curing) 4 a, 4 b, 4 c, and 4 d for each print. The recording medium2 is transferred from left to right in FIG. 3. The reference numeral 6represents a printed matter reeling roll.

The printing unit 3 a, 3 b, 3 c and 3 d optionally have heatingmechanisms at ink discharging portions to lower the viscosity of ink.For workability after printing, a processing unit 5 can be optionallyprovided to proceed working such as perforation, marginal punch holes,filing punch holes, and corner cutting.

The recording medium 2 is formed of paper, film, metal, or mixturesthereof. In addition, although the recording medium 2 has a roll form inFIG. 3, a sheet form is also suitable Also, duplex printing is possible.Curability is improved by irradiation of ultraviolet ray whenever eachcolor is printed for high speed performance. On the other hand, thepower of the ultra violet ray light sources 4 a, 4 b, and 4 c isweakened or zero and multiple colors are irradiated and cured by theultra violet ray light source 4 d after some or all of the colors areprinted to lower the cost and save energy.

Having generally described preferred embodiments of this invention,further understanding can be obtained by reference to certain specificexamples, which are provided herein for the purpose of illustration onlyand are not intended to be limiting. In the descriptions in thefollowing examples, the numbers in parts represent weight ratios inparts unless otherwise specified.

EXAMPLES

The present invention is described in detail with reference to theExamples but not limited to the following Examples.

Comparative Example 1

Ink composition of Comparative Example 1 was obtained by mixing thefollowing materials.

Dipentaerythritol penta/hexaacrylate (M-405, manufactured  20 parts. byToagosei Company, Limited, no skin sensitization data): Trimethylolpropane triacrylate (M-309, manufactured by 10 parts Toagosei Company,Limited, skin sensitization causing material mentioned in MSDS):Propylene oxide modified neopentyl glycol diacrylate 20 parts (SR9003,manufactured by Sartomer Company Inc., SI value: 3.7): Neopentyl glycoldimethacrylate (NPG, manufactured by 10 parts Shin-Nakamura ChemicalCo., Ltd., SI value: 2.0): Triethylene glycol divinylether (DVE3,manufactured by 40 parts BASF, no skin sensitization mentioned in MSDS):Photoradical polymerization initiator (2-dimmethylamino-2- 10 parts(4-methyl-benzyl)-1-(4-morpholine-4-yl-phenyl)butane-1-one) (no skinsensitization mentioned in MSDS): Radical polymerization inhibitor(t-butyl hydroquinone): 0.1 parts 

Comparative Example 2

Ink composition of Comparative Example 2 was prepared in the same manneras in Comparative Example 1 except that 1 part by weight of N-methyldiethanol amine was added to the ink composition of Comparative Example1.

Comparative Example 3

Ink composition of Comparative Example 3 was prepared in the same manneras in Comparative Example 1 except that 2 part by weight of N-methyldiethanol amine was added to the ink composition of Comparative Example1.

Comparative Example 4

Ink composition of Comparative Example 4 was prepared in the same manneras in Comparative Example 1 except that 5 part by weight of N-methyldiethanol amine was added to the ink composition of Comparative Example1.

Example 1

Ink composition of Example 1 was prepared in the same manner as inComparative Example 1 except that 1 part by weight of 1 mol/l of aqueoussolution of potassium hydroxide (0.03 parts by weight as potassiumhydroxide) was added to the ink composition of Comparative Example 0.5.

Example 2

Ink composition of Example 2 was prepared in the same manner as inComparative Example 1 except that 1 part by weight of 1 mol/1 of aqueoussolution of potassium hydroxide (0.06 parts by weight as potassiumhydroxide) was added to the ink composition of Comparative Example 1.

Example 3

Ink composition of Example 3 was prepared in the same manner as inComparative Example 1 except that 0.5 parts by weight of 1 mol/l ofaqueous solution of sodium hydroxide (0.02 parts by weight as sodiumhydroxide) was added to the ink composition of Comparative Example 1.

Example 4

Ink composition of Example 4 was prepared in the same manner as inComparative Example 1 except that 1 parts by weight of 1 mol/l ofaqueous solution of sodium hydroxide (0.04 parts by weight as sodiumhydroxide) was added to the ink composition of Comparative Example 1.

Example 5

Ink composition of Example 5 was prepared in the same manner as inExample 1 except that 1 part by weight of N-methyl diethanol amine wasadded to the ink composition of Example 1.

Example 6

Ink composition of Example 6 was prepared in the same manner as inExample 2 except that 1 part by weight of N-methyl diethanol amine wasadded to the ink composition of Example 2.

Example 7

Ink composition of Example 7 was prepared in the same manner as inExample 3 except that 1 part by weight of N-methyl diethanol amine wasadded to the ink composition of Example 3.

Example 8

Ink composition of Example 8 was prepared in the same manner as inExample 4 except that 1 part by weight of N-methyl diethanol amine wasadded to the ink composition of Example 4.

Comparative Example 5

Ink composition of Comparative Example 5 was obtained by mixing thefollowing materials.

Caprolactone modified dipentaerythritol hexaacrylate (DPCA 20 parts  60,manufactured by Nippon Kayaku Co., Ltd., Negative in MSDS): Ethyleneoxide-modified bisphenol A diacrylate (BPE10, 10 parts  manufactured byDAI-ICHI KOGYO SEIYAKU CO., LTD., SI value = 1.2): Polyethoxylatedtetramethylol methane tetraacrylate 5 parts (ATM35E, manufactured byShin-Nakamura Chemical Co., Ltd., SI Value = 1.7): Diacrylate ofcaprolactone-modified hydroxy pivalic acid 5 parts neopentyl glyco(HX620, manufactured by Nippon Kayaku Co., Ltd., SI Value = 0.9):Hydroxyethyl acrylic amide (HEAA, manufactured by Kohjin 2 partsHoldings Co., Ltd., No skin sensitization in MSDS): Polypropylene glycol(n = 12) diacrylate (M-270, 5 parts manufactured by Toagosei Company,Limited, SI value = 1.5): Polyethylene glycol (n = 14) dimethacrylate(Light Ester 1 part  14EG, manufactured by Kyoeisha Chemical Co. LTD.,SI value: 1.6): Polyethylene glycol (n = 9) dimethacrylate (Light Ester9EG, 1 part  manufactured by Kyoeisha Chemical Co. LTD., SI value: 1.3):Trimethylol propane triacrylate (SR-350, manufactured by 2 partsSartomer Company Inc., SI value 1.9): γ-butyloactone methacrylate(GBLMA, manufactured by 1 part  OSAKA ORGANIC CHEMICAL INDUSTRY LTD., SIvalue: 2.1): Staryl acrylate (STA, manufactured by OSAKA ORGANIC 2 partsCHEMICAL INDUSTRY LTD., SI value: 2.7): Neopentyl glycol dimethacrylate(NPG, manufactured by 2 parts Shin-Nakamura Chemical Co., Ltd., SIvalue: 2.0): 1,4-butane diol dimethacrylate (SR214, manufactured by 2parts Sartomer Company Inc.: SI value = 2.6): Tricyclodecane dimethanoldimethacrylate (DCP, 2 parts manufactured by Shin-Nakamura Chemical Co.,Ltd., SI value: 1.3): Triethylene glycol divinylether (DVE3,manufactured by 40 parts  BASF, no skin sensitization mentioned inMSDS): Photoradical polymerization initiator (2-dimmethylamino-2- 10parts  (4-methyl-benzyl)-1-(4-morpholine-4-yl-phenyl)butane-1-one) (noskin sensitization mentioned in MSDS): Radical polymerization inhibitor(t-butyl hydroquinone): 0.1 parts 

Comparative Example 6

Ink composition of Comparative Example 6 was prepared in the same manneras in Comparative Example 5 except that 1 part by weight of N-methyldiethanol amine was added to the ink composition of Comparative Example5.

Comparative Example 7

Ink composition of Comparative Example 7 was prepared in the same manneras in Comparative Example 5 except that 2 part by weight of N-methyldiethanol amine was added to the ink composition of Comparative Example5.

Comparative Example 8

Ink composition of Comparative Example 8 was prepared in the same manneras in Comparative Example 5 except that 5 part by weight of N-methyldiethanol amine was added to the ink composition of Comparative Example5.

Example 9

Ink composition of Example 9 was prepared in the same manner as inComparative Example 1 except that 5 part by weight of 1 mol/l of aqueoussolution of potassium hydroxide (0.03 parts by weight as potassiumhydroxide) was added to the ink composition of Comparative Example 0.5.

Example 10

Ink composition of Example 10 was prepared in the same manner as inComparative Example 5 except that 1 part by weight of 1 mol/l of aqueoussolution of potassium hydroxide (0.06 parts by weight as potassiumhydroxide) were added to the ink of Comparative Example 5.

Example 11

Ink composition of Example 11 was prepared in the same manner as inComparative Example 5 except that 0.5 parts by weight of 1 mol/l ofaqueous solution of sodium hydroxide (0.02 parts by weight as sodiumhydroxide) was added to the ink composition of Comparative Example 0.5.

Example 12

Ink composition of Example 12 was prepared in the same manner as inComparative Example 5 except that 1 part by weight of 1 mol/l of aqueoussolution of sodium hydroxide (0.04 parts by weight as sodium hydroxide)were added to the ink of Comparative Example 5.

Example 13

Ink composition of Example 13 was prepared in the same manner as inExample 9 except that 1 part by weight of N-methyl diethanol amine wasadded to the ink composition of Example 11.

Example 14

Ink composition of Example 14 was prepared in the same manner as inExample 10 except that 1 part by weight of N-methyl diethanol amine wasadded to the ink composition of Example 10.

Example 15

Ink composition of Example 15 was prepared in the same manner as inExample 11 except that 1 part by weight of N-methyl diethanol amine wasadded to the ink composition of Example 11.

Example 16

Ink composition of Example 16 was prepared in the same manner as inExample 12 except that 1 part by weight of N-methyl diethanol amine wasadded to the ink composition of Example 12.

The ink composition prepared as described above was sealed in a samplebottle, heated to 70° C., and left for 14 days as an acceleration test.Storage stability was evaluated by confirming the viscosity change fromthe initial state. Viscosity was measured by a cone plate type rotationviscosity meter manufactured by TOKI SANGYO CO., LTD. The constanttemperature circulation water was set to 25° C. and the viscosity change(%) from the initial state was shown. The smaller the viscosity change,the better the storage stability.

The evaluation results are shown in Tables 1 and 2.

TABLE 1 Alkali component Storage stability (parts by weight) (viscositychange) Comparative None Gel. Unable to Example 1 measure viscosityComparative N-methyl diethanol  +20% Example 2 amine (1) ComparativeN-methyl diethanol  +16% Example 3 amine (2) Comparative N-methyldiethanol +9.0% Example 4 amine (5) Example 1 1 mol/L of potassium +1.5%hydroxide (0.5) Example 2 1 mol/L of potassium +1.2% hydroxide (1)Example 3 1 mol/L of sodium +1.8% hydroxide (0.5) Example 4 1 mol/L ofsodium +1.4% hydroxide (1) Example 5 N-methyl diethanol +1.0% amine (1)1 mol/L of potassium hydroxide (0.5) Example 6 N-methyl diethanol +0.6%amine (1) 1 mol/L of potassium hydroxide (1) Example 7 N-methyldiethanol +1.2% amine (1) 1 mol/L of sodium hydroxide (0.5) Example 8N-methyl diethanol +0.8% amine (1) 1 mol/L of sodium hydroxide (1)

TABLE 2 Alkali component Storage stability (parts by weight) (viscositychange) Comparative None Gel. Unable to Example 5 measure viscosityComparative N-methyl diethanol  +15% Example 6 amine (1) ComparativeN-methyl diethanol  +10% Example 7 amine (2) Comparative N-methyldiethanol +8.0% Example 8 amine (5) Example 9 1 mol/L of potassium +1.1%hydroxide (0.5) Example 10 1 mol/L of potassium +0.9% hydroxide (1)Example 11 1 mol/L of sodium +1.2% hydroxide (0.5) Example 12 1 mol/L ofsodium +0.8% hydroxide (1) Example 13 N-methyl diethanol +1.0% amine (1)1 mol/L of potassium hydroxide (0.5) Example 14 N-methyl diethanol +0.2%amine (1) 1 mol/L of potassium hydroxide (1) Example 15 N-methyldiethanol +0.9% amine (1) 1 mol/L of sodium hydroxide (0.5) Example 16N-methyl diethanol +0.2% amine (1) 1 mol/L of sodium hydroxide (1)

As seen in the results of Examples, according to the present disclosure,a low viscous polymerizable ink composition is provided which hasexcellent curability and excellent storage stability while being freefrom skin sensitization problems.

Having now fully described embodiments of the present invention, it willbe apparent to one of ordinary skill in the art that many changes andmodifications can be made thereto without departing from the spirit andscope of embodiments of the invention as set forth herein.

What is claimed is:
 1. A polymerizable ink composition comprising:polymerizable monomers comprising: at least one of an acrylic acid estercompound, a methacrylic acid ester compound, an acryl amide, and amethacryl amide; and a vinyl ether compound; and one of potassium oxideand sodium oxide.
 2. The polymerizable ink composition according toclaim 1, further comprising water.
 3. The polymerizable ink compositionaccording to claim 1, further comprising N-methyl diethanol amine. 4.The polymerizable ink composition according to claim 1, wherein at leastone of the at least one of an acrylic acid ester compound, a methacrylicacid ester compound, an acryl amide, and a methacryl amide comprises 1to 6 functional groups.
 5. The polymerizable ink composition accordingto claim 1, wherein the polymerizable monomer has a Stimulation Index(SI) of less than 3 as measured by a skin sensitization test by LocalLymph Node Assay (LLNA) Method.
 6. The polymerizable ink compositionaccording to claim 5, wherein the polymerizable monomer having an SIvalue of less than 3 is at least one of: polyetylene glycoldimethacrylate represented by a chemical formula 1:CH₂═C(CH)₃CO—(OC₂H₄)_(n)—OCO—C(CH₃)═CH₂ (where n=9 to 14, where nrepresents an average polymerization degree), γ-butylolactonemethacrylate, trimethylol propane trimethacrylate, tricyclodecanedimethanol dimethacrylate, caprolactone modified dipenta erythritolhexaacrylate, polypropylene glycol diacrylate represented by a chemicalformula 2: CH₂═CH—CO—(OCH₃H₆)_(n)—OCOCH═CH₂ (n=12, where n represents anaverage polymerization degree), diacrylate of caprolactone-modifiedhydroxy pivalic acid neopentyl glycol ester represented by the followingchemical relation A:

where m and n represent average polymerization degree and m+n=4,polyethoxylated tetramethylol methane tetraacrylate, ethyleneoxide-modified bisphenol A diacrylate, neopentyl glycol dimethacrylate,stearyl acrylate, 1,4-butane diol dimethacrylate, and hydroxyethylacrylamide.
 7. The polymerizable ink composition according to claim 1,wherein the vinyl ether compound is triethylene glycol divinyl ether. 8.The polymerizable ink composition according to claim 1, furthercomprising a photoradical polymerization initiator.
 9. An ink cartridgecomprising: a container; and the polymerizable ink composition of claim1 that is accommodated in the container.
 10. An inkjet printercomprising: a printing unit comprising: the polymerizable inkcomposition of claim 1; and a radiation source irradiation unit.
 11. Aninkjet printer comprising: a printing unit; and a radiation sourceirradiation unit, wherein the ink cartridge of claim 9 is installed inthe inkjet printer.